Peyton Manning went virtually untouched by Kansas City's defense as he threw for 323 yards and a touchdown to lead the Denver Broncos to a 27-17 victory over what had been the NFL's last undefeated team.
The Chiefs, who came into the game with a league-leading 36 sacks, barely breathed on Manning, who finished 24 for 40.
The Broncos equalled Kansas City at 9-1 atop the American Football Conference West with a rematch set in two weeks.
Alex Smith threw for 230 yards and two touchdowns for Kansas City, which hadn't lost since a 38-3 setback in Denver last December to close out a 2-14 season.
The Chicago Bears downed the Baltimore Ravens 23-20 after Robbie Gould kicked a 38-yard field goal in a game delayed about two hours by a torrential downpour.
Justin Tucker levelled it for the Ravens with a 21-yard field goal at the end of regulation.
The big delay came after Tucker kicked a 52-yard field goal with 4:51 remaining in the first quarter. Fans were ordered to take cover and players headed to the locker rooms as heavy rains and winds whipped through Soldier Field.
They emerged about two hours later with the sky clearing and the sun coming out, but the rain and wind returned in the third quarter, turning the stands into a sea of ponchos.
Marques Colston capped a record-setting day with a 20-yard reception to get the Saints into field goal range and Garrett Hartley kicked a 31-yarder as time expired to lift New Orleans over the San Francisco 49ers 23-20.
Hartley, who had missed four field goals in the Saints' previous three games, made all three of his field goal attempts in the fourth quarter. He earlier hit from 21 and 42 yards.
At Philadelphia, Nick Foles threw for 298 yards and ran for a touchdown, and LeSean McCoy had two TDs rushing as the Eagles broke a 10-game home losing streak with a 24-16 win over the Washington Redskins.
A year after finishing 4-12 under Andy Reid, Chip Kelly's Eagles (6-5) are first in the NFC East. They're a half-game ahead of Dallas, who had a bye. The defending division champion Redskins fell to 3-7.
The Eagles hadn't won at the Linc in 413 days since defeating the New York Giants on September 30, 2012.
Cincinnati's Andy Dalton threw two touchdown passes as the Bengals returned a blocked punt and a fumble for touchdowns during a 31-point second quarter that set a club record.
The Bengals (7-4) head into their bye week with their division lead intact. They'd lost their last two games in overtime, tying the NFL record and allowing the Browns (4-6) to draw close.
Ben Roethlisberger passed for 367 yards and four touchdowns, including two in the final 5 minutes as the Pittsburgh Steelers rallied to beat the Detroit Lions 37-27, while Jairus Byrd had two interceptions to lead a Buffalo
defense that forced four turnovers in the Bills' 37-14 victory over the New York Jets.
Oakland rookie Matt McGloin threw three touchdown passes in his first NFL start as the Raiders beat the Houston Texans 28-23, while Carson Palmer threw for 419 yards and two scores and did not throw an interception for the first time all year to lead the Arizona Cardinals over the Jacksonville Jaguars 27-14.
In other games, the Tampa Bay Buccaneers downed the Atlanta Falcons 41-28, the New York Giants defeated the Green Bay Packers 27-13, the Seattle Seahawks beat the Minnesota Vikings 41-20 and the Miami Dolphins were 20-16 winners over the San Diego Chargers.